Hydroconversion of solid carbonaceous materials



Jan- 29 1963 Du Bols EAsTMAN ETAL 3,075,912

HYDROCONVERSION OF SOLID CARBONACEOUS MATERIALS Filed sept. 18. 195eUnite 3,075,912 HYDROCONVERSION F SOLID CARBO- NACEOUS MATERIALS Du BoisEastman, Whittier, and Warren G. Schlinger,

Pasadena, Calif., assignors to Texaco Inc., a corporation of DelawareFiled Sept. 18, 1953, Ser. No. 761,772 3 Claims. (Cl. 208-8) Thisinvention relates to the hydroconversion of solid carbonaceousmaterials. The process of the present invention is particularlyapplicable to the treatment of coal and may be applied to thehydrogenation of anthracite, bituminous coal or lignite. In its morespecific aspects, this invention relates to the production of valuableliquids such as fuels for internal combustion engines.

Prior attempts to convert solid carbonaceous materials such as coal intovaluable liquid products by hydrogenation have not proven satisfactory.Because of the high pressures which are required and the long reactiontimes, the equipment necessary for carrying out the reaction has beenexpensive and cumbersome, e.g. a commercial reactor large enough toallow a reaction time of 3-4 hours would have `an internal diameter of32 inches and a wall thickness Aof about 8 inches. In addition, the useof a catalyst has presented several problems. Fixed bed catalysts haveproven impractical because of the nature of `the material 'beingtreated. The use of a iinely divided catalyst suspended in the reactionmedium has proven costly because of the ineiciency of the knownhydrogenation methods. The catalyst rapidly became deactivated by beingcoated with asphalt and after one pass through the reaction zone hadtobe discarded. Also, because of .the inetliciency of Aknown methods, itwas necessary, for 'the production of lighter hydrocarbon liquids tohydrogenate the coal in one reactor using a finely divided catalyst,separate the heavy liquid product from the ash and contaminatedcatalyst, add fresh catalyst'to the heavy liquid product and thensubject it to additional hydrogenation in a second reactor to Vproduce aliquid boiling in the gasoline range.

It is an object of the present invention to provide an improved processfor the hydrogenation of a solid carbonaceous material.

Another object of the present invention is to provide `an improvedprocess for the production of valuable liquids from coal by reaction ofthe powdered coal with hydrogen.

Still another object is to provide an improved process for theproduction of motor fuels from coal by a non- .catalytic hydrogenationprocess.

In accordance with the process ofthe present invention the solidcarbonaceous material such as coal is tinely divided, slurried in aliquid medium such as water ory oil and passed in contact with hydrogenthrough a reactor under conditions of highly turbulent flow to producevaluable liquid products.

Any solid carbonaceous material Vmay be suitably treated by the processof the present invention. Such materials as anthracite, anthracite silt,bituminous coal, lignite, peat, sawdust and the like are satisfactoryfeed stocks. The solid carbonaceous'material which will be referred toas'coal in the following general description of the invention ispulverized to an average particle size vof about -60 mesh and is thenslurried with a suitable liquid medium which is inert or only slightlyreactive under reaction conditions such as water or an oil which mayserve as a hydrogen donor. Preferably, theslurrying Ymedium used informing the suspension is a hydrogenated aromatic or an oil mixturecomprising hydroaromatics which act as hydrogen transfer agents.Hydroaromatics which are suitable yfor use in the process includetetralin and decalin. The heavy-oil or middle distillate which areobtained from the hydrogenation of the coal are especially suited forthe preparation of the feed mixture and contain hydroaromatics. Ifdesired, a fraction separated from the heavy oil product or a suitablefraction of oil from another source may be used in the preparation ofthe feed slurry. The slurry will usually contain at least 'about 35% byweight of liquid. To maintain the liquid particles in suspension, theliquid slurry should be maintained at a velocity of aboutl to 10 feetper second depending on the slurry medium and on the average particlesize. i

The reaction in which the coal is hydrogenated is carried out inatubular reactor'having a length of at least 100 and preferably at leasttimes the maximum cross sectional dimension of the reactor.

The hydrogen used in the process of the present invention may beIderived from any suitable source. Electrolytic hydrogen or hydrogenobtained by the partial combustion of carbonaceous materials has provensatisfactory. Materials suitable for feed stock to a partial combustiongas generator are powdered solid carbonaceous materials, liquidhydrocarbons or gaseous hydrocarbons. Heavy liquid hydrocarbons andhydrocarbon gases which are produced by the hydrogenation of solidcarbonaceous materials are particularly desirable. When solidcarbonaceous materials containing volatile substances are used as feedstock vto thegas generator, the materials volatilized during thepreheating of the solid carbonaceous vmaterial may be removed and, ifdesired, included inthe feed to the -hydrogenation unit. When materialscontaining large amounts of moisture such as lignite are used as feedstock for the gas generation, after preheating, a portion of the steamshouldbe removed prior to the introduction of the feed into thegenerator to prevent the introduction of excessive amounts of steam intothe gas generatorA The hydrogen used in the hydrogenation step may beinrelatively pure form or may be used in concentrations as low vas 25volume percent. Synthesis gas, i.e. a mixture vof carbon monoxide andhydrogen such as that obtained by the methods disclosedin U.S. Patents2,582,938 Vand 2,669,509 may be used satisfactorily.

Reaction times may range from 1 second to 2 hours but reaction times of20 to 300 seconds are preferred. Teniperatures of 700vto l500 F.,preferably between about 900 and 1100" F. may be employed.Superatmospheric pressures ranging from 500 to 20,000 p.s.i.g. Yandhigher may be used although pressures of 1500 to 10,000 p.s.i.g. arepreferred. Hydrogen rates may range from 1000 to 100,000 standard cubicfeet per barrel of slurry feed, rates of 2000 to 50,000 standard cubicfeet per barrel-of slurry feed being preferred. Y

For the hydrogenation of the coal to be'effectve Ythe reaction mixturemust be maintained/during the reaction, .under conditions of highturbulence. The slurry feed rate, hydrogenl recycle rate, reaction coildiameter and operating conditions of .temperature and pressure all tendto aect the velocity of ow and the turbulence. It has been foundconvenient to express turbulence in terms of the ratio of the averageapparent viscosity of the owing stream, 2m, to the molecularor kinematicviscosity v, viz. 2m

Hereinafter, we shall refer to this ratio as turbulence level. Theapparent viscosity of the owing stream, em, equals fthe sum of the eddyviscosity, em,

and the kinematic viscosity v which may be shown in the expressionem=emlv. Under conditions of turbulence,

em, has a finite value and it is apparent that if the magnitude of theapparent viscosity exceeds the kinematic viscosity at `the point inquestion, that the ratio of exceeds unity. The average apparentviscosity, gm, as employed hereinis dened by the equation where ro isthe radius of the conduit. By substitution and integration, employingthe parameters described by Corcoran et al., Industrial and EngineeringChemistry, 44, 410 (1952), this expression The latter equation is interms which may be readily determined for a given system; ro being theconduit radius, a the specific weight of the owing fluid, g theacceleration of gravity and the pressure drop per unit of conduitlength. In the pro-cess of this invention, turbulence levels of andhigher may be employed but turbulence levels of 50 to 1000 arepreferable. At turbulence levels below 25, a heavy tarlike material isformed at the expense of the desired products. 'Ihis tar-like materialalso causes fouling and plugging of the apparatus requiring frequentshut-downs.

In the foregoing paragraph, the various symbols used in the formulas aredelned as follows:

d=dilerential g= acceleration of gravity, feet per second p=pressure,pounds per square foot r=radial distance from center of conduit, feetr0=radius of conduit, feet x=distance, feet em=eddy viscosity, squarefeet per second emr-apparent viscosity, square feet per second may berewritten em=average apparent viscosity, square feet per second Theinvention may be better understood by referring to the accompanyingdrawing which represents diagrammatically a flow scheme `for thepractice of the present invention. Y

Coal is introduced through line 21 to grinding mechanism 22 where it ispulverized to an average particle size o-f below about 60 mesh. Thepowder is transferred through line 23 to mixing chamber 24 wherein it ismixed with oil introduced through line 25. The coal oil slurry is thentransferred through line and with hydrogen from line 31 isintroducedinto preheater 32 where the temperature is raised 'to about SOO-600 F.

aendern The heated slurry and hydrogen are then passed through line 33to hydrogenation unit 34 Where they are subjected to highly turbulentow. The hydrogenation product is removed from hydrogenation unit 34through line 35 and introduced into hot separator 36 where gaseousmaterial is separated from the liquid product. The liquid product istransferred to let down tank 40 through line 41. In let down tank 40,the pressure is reduced and a separation is effected between the heavyoil and the oil saturated residue. The heavy oil is removed from letdown tank dit through line 43 and may be returned to slurry tank 24through lines 46 and 25 or sent to gas generator 80 by means of lines43, 38 and 81. The heavy oil saturated ash is sent to ash separator 50through line 51 Where the heavy oil is separated to a large extent fromthe ash which is removed from ash separator 50 through line 52, the oilbeing withdrawn through line 79. Ash separator 50 may be either in theform of a centrifuge or in the form of a separating tank containing alower layer of water. In either case, dilution of the heavy oil with alighter oil is preferred in the irst case to facilitate the removal ofthe ash and in the second case to minimize the possibility of theformation of oil-water emulsions. The overhead from hot separator 36 iswithdrawn through line 61 and after cooling in a heat exchanger (notshown) is sent to cold separator 62 from which hydrogen is withdrawnthrough line 31 and returned to preheater 32 through line 30. The liquidhydrogenation product is removed from cold separator 62 through line 63and introduced into fractionator 64 wherein a separation is made oflight hydrocarbon gases withdrawn through line 65, a motor fuel fractionwithdrawn through line 66, a middle distillate fraction withdrawnthrough line 67 and a residual fraction withdrawn through line 68. Whena portion of the middle distillate is used to dilute the heavy residuewithdrawn from let down tank 40 through line 51 it is sent through lines67, 81, 46, 70 and 51 to ash separator 50 Where it facilitates theseparation of the heavy oil from the ash. If desired, a portion of themiddle distillate from fractionator 64 may be used to form a slurry ofthe coal feed, in which case it is sent to mixing chamber 24 throughlines 67, 81, 46 and 25.

Hydrogen for the process is preferably supplied by partial combustion ofthe heavy liquid products resulting from the hydrogenation of the coal.Heavy oil from ash separator 50 for the bottoms from fractionator 64 ora portion of the middle distillate from fractionator 64 may be sent togenerator through lines 79 and 81, 68 and 81 or 67 and 81 respectivelyor a mixture thereof may be used as feed to gas generator 80. Steam fromline 84 and oxygen from line 85 are also introduced into gas generator80 where the oil is subjected to partial combustion. The products areremoved from generator 80 through line 89 and partially cooled in heatrecovery unit 85, which may be, for example, a heat exchanger in whichthe hot gaseous products are passed in indirect heat exchange withwater. The resulting steam may be used as a source of power for thegrinding operation. The product gases then may be sent through topreheater 32 by rneans of lines 86, 87, 90 and 30 or if a highconcentration of hyodrogen is desired, may be subjected to a water gasshift in shift reactor 91 Where the partial conibustion products arecontacted with an iron oxide catalyst in the presence of steam, thecarbon monoxide reacting with steam to produce carbon dioxide andadditional hydrogen. The shifted gas is transferred through line 92 toscrubber 93 wherein the gas is contacted with an amine solution for theremoval of CO2 and a gas containing about 95% hydrogen is removed andsent to preheater 32 through lines 90 and 30.

The following example is given for illustrative purposes only and itshould be understood that the invention is not limited thereto.

A slurry composed of 10 parts by weight of bituminous coal pulverized toa particle size of -60 mesh and 11 parts by weight of a middledistillate, the source of which will be explained later, is mixed with10,000 cubic feet of a gas containing 80% hydrogen per barrel of slurry.The mixture is passed through a tubular reactor at a temperature of 950F., a pressure of 5000 p.s.i.g., a reaction time of 50 seconds and at aturbulence level of 450. The hydrogen containing gas is made up of 7640standard cubic feet of recycle gas and 2360 standard cubic feet ofmake-up hydrogen having a purity of 95%. After hot and cold separation,let down, centrifuging and fractionating, the products obtained per 100lb. of coal feed are as follows:

Hydrogen consumption amounts to 1400 standard cubic feet per 100 lb.coal feed.

Of the 130 pounds of middle distillate, 110 pounds is recycled per 1001b. of coal feed to make up additional slurry, pounds is withdrawn tostorage and the remaining 10 pounds together with 20.5 pounds of heavyoil are charged with 15.2 pounds of steam and 31.5 pounds of oxygen to asynthesis gas generator. The gas generator is opera-ted at 290 p.s.i.g.and 2400 F. After quenching, the eiiluent gases are passed to a shiftconverter and then contacted with an amine scrubber. The product gasamounts to 1400 standard cubic feet of 98% purity hydrogen which is usedas make up for the hydrogenation unit. The gasoline produced has thefollowing characteristics.

This gasoline may be upgraded, by catalytic reforming, to produce amotor fuel having a leaded octane number of about 100.

Obviously, many other modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. A process for the hydroconversion of a solid carbonaceous materialwhich comprises forming a slurry of said solid carbonaceous materialwith a hydrocarbon liquid boiling in the middle distillate range,passing said slurry as a confined stream through a hydrogenation zonemaintained at a temperature between about 700 and 1500 F., a pressurebetween -about 1500 and 10,000 p.s.i.g. and a turbulence level ofbetween about 50 and 1000 in the presence of hydrogen, separating theeluent from said hydrogenation zone into a gas containing hydrogen, afraction containing hydrocarbon gases, a fraction boiling in the motorfuel range, a fraction boiling in the middle distillate range and aheavy oil, recycling said gas containing hydrogen to the hydrogenationzone, recycling at least a portion of said fraction boiling in themiddle distillate range to form additional slurry, forming a secondslurry `of finely-divided solid carbonaceous material with at least aportion of said heavy oil, subjecting said second slurry to partialcombustion to produce agas containing hydrogen and carbon monoxide,blending a portion of said gas containing hydrogen and carbon monoxidewith said fraction containing hydrocarbon gases to produce a gassuitable for use as a heating gas, subjecting the balance of said gascontaining hydrogen and carbon monoxide to a water gas shift reaction toproduce a hydrogen rich gas and introducing said hydrogen rich gas intothe hydrogenation zone as make-up hydrogen.

2. The process of claim l in which the temperature is 900-1100 F.

3. The process of claim 1 in which the solid carbonaceous materialcomprises coal.

References Cited in the file of this patent UNITED STATES PATENTS1,458,983 Kirby June 19, 41923 1,888,998 Mercier Nov. 29, 1932 2,007,226Szayna July 9, 1935 2,207,494 Viktora July 9, 1940 2,639,982 Kalbach May26, 1953 2,658,861 Pevere et al Nov. 10, 1953 2,753,296 Sellers July 3,1956 2,793,104 Rees May 21, 1957 2,885,337 Keith et a-l May 5, 19592,989,461 Eastman et al. June 20, 1961

1. A PROCESS FOR THE HYDROCONVERSION OF A SOLID CARBONACEOUS MATERIALWHICH COMPRISES FORMING A SLURRY OF SAID SOLID CARBONACEOUS MATERIALWITH A HYDROCARBON LIQUID BOILING IN THE MIDDLE DISTILLATE RANGE,PASSING SAID SLURRY AS A CONFINED STREAM THROUGH A HYDROGENATION ZONEMAINTAINED AT A TEMPERATURE BETWEEN ABOUT 700 AND 1500*F., A PRESSUREBETWEEN ABOUT 1500 AND 10,000 P.S.I.G. AND A TURBULENCE LEVEL OF BETWEENABOUT 50 AND 1000 IN THE PRESENCE OF HYDROGEN, SEPARATING THE EFFLUENTFROM SAID HYDROGENATION ZONE INTO A GAS CNTAINING HYDROGEN, A FRACTIONCONTAINING HYDROCARBON GASES, A FRACTION BOILING IN THE MOTOR FUELRANGE, A FRACTION BOILING IN THE MIDDLE DISTILLATE RANGE AND A HEAVYOIL, RECYCLING SAID GAS CONTAINING HYDROGEN TO THE HYDROGENATION ZONE,RECYCLING AT LEAST A PORTION OF SAID RRACTION BOILING IN THE MIDDLEDISTILLATE RANGE TO FORM ADDITIONAL SLURRY, FORMING A SECOND SLURRY OFFINELY-DIVIDED SOLID CARBONACEOUS MATERIAL WITH AT LEAST A PORTION OFSAID HEAVY OIL, SUBJECTING SAID SECOND SLURRY TO PARTIAL COMBUSTION TOPRODUCE A GAS CONTAINING HYDROGEN AND CARBON MONOXIDE, BLENDING APORTION OF SAID GAS CONTAINING HYDROGEN AND CARBON MONOXIDE WITH SAIDFRACTION CONTAINING HYDROCARBON GASES TO PRODUCE A GAS SUITABLE FOR USEAS A HEATING GAS, SUBJECTING THE BALANCE OF SAID GAS CONTAINING HYDROGENAND CARBON MONOXIDE TO A WATER GAS SHIEFT REACTION TO PRODUCE A HYDROGENRICH GAS AND INTRODUCING SAID HYDROGEN RICH GAS INTO THE HYDROGENATIONZONE AS MAKE-UP HYDROGEN.